The high mortality rate for patients with newly diagnosed colorectal cancer is based on the low percentage of localized disease at the time of surgery. No further benefit appears to be forthcoming in the patients with the current approach of diagnosis in symptomatic patients. Improved survival may be possible by screening asymptomatic patients at risk with currently available fecal occult blood tests coupled with available sensitive radiologic and endoscopic diagnostic techniques. Evaluation of this approach requires controlled trials for demonstration of a screening benefit. Longterm followup for survival data is critical to this evaluation. Our controlled trial has been ongoing for 5 years with entry of approximately 20,000 patients in screened and control groups with approximately 40,000 examinations performed to date. Our data suggest that screening with fecal occult blood testing is feasible, with high patient compliance in a well-motivated population, low manageable rate of positive slides, low false-positivity for neoplasia, high predictive value for neoplasia, and favorable staging of detected cancers in symptomatic screened group. The continuation of our program will focus on followup of patients who have had colon cancer detected for survival data and followup of all patients for mortality data in the control and screened groups. Additional evaluation will include: continued evaluation of the Hemoccult slide technique; evaluation of factors that influence patient compliance; evaluation of cost factors; continued evaluation of additional detected cancers; continued evaluation of diagnostic techniques; and continued evaluation of significance of adenoma detection and removal. The higher level of funding requested is to support the large effort necessary to successfully follow the 25,000 patients entered into the study, for mortality data, interval cancers, interval adenomas, yield of rescreening, and cancer incidence data. No new patients are being entered.